Just Enough of a Good Thing If you eat raw oysters and cabbage every day, we know two things about you: 1) That's kind of an unusual diet you've got going there, and 2) You're getting quite a bit of zinc in your diet. In fact, you might be getting too much (more on that in a moment). But according to a new study, the right amount of zinc provides some very healthy benefits - especially as you get on in years. Sing it First we'll sing the praises of zinc, one of the key nutrients needed for DNA reproduction and repair: - Zinc is an antioxidant and anti-inflammatory
- Zinc enhances the immune system and helps repair damaged tissues
- Zinc inhibits abnormal blood clotting that contributes to heart disease
- Zinc helps maintain healthy vision and reduces the risk of age-related macular degeneration
In the March issue of the American Journal of Clinical Nutrition, a team led by researchers at the Wayne State University School of Medicine reported on a study that reveals another important zinc benefit. STUDY PROFILE - The authors note that zinc deficiency, susceptibility to infections, and increased oxidative stress are common in people over the age of 55
- Fifty healthy subjects between the ages of 55 and 87 were recruited
- When these subjects were compared to a group of younger subjects before the study began, researchers found that the older group generally had lower blood levels of zinc, and higher amounts of inflammatory and oxidative stress markers
- For one year, half the subjects received a daily zinc supplement (45 mg) and half received a placebo
- Over the course of the intervention period, incidence of infections was significantly lower in the zinc group, compared to placebo
- Tests conducted at the conclusion of the intervention period showed that subjects in the zinc group had higher blood levels of zinc, and reduced markers for inflammation and oxidative stress
In an interview with NutraIngredients, researcher David Richardson noted that energy intake declines as we age, which makes it "much more difficult to ensure the micronutrient intake of the diet as a whole." Apalachicola Blues Now…about those oysters… You can get respectable amounts of zinc in red meat, poultry, beans, nuts, whole grains and dairy products, but none of these come close to the high zinc levels in oysters. The zinc content of cabbage places second, but it's a very distant second. According to the web site NutritionData (nutritiondata.com - a truly exhaustive source of nutrition information for thousands of specific food items), the zinc in oysters ranges from 40 mg to nearly 280 mg per every 200 calories consumed. Pacific oysters are in the low range, and "eastern" oysters provide the high range. In addition, oysters are a good source of vitamins D, A, and B-12, as well as EPA and DHA omega-3 fatty acids. But all of this good nutrition drops off sharply if oysters are battered and fried - no surprise there. But let's suppose you're an oyster-lover who lives on Apalachicola Bay in the Florida panhandle and you indulge in a dozen or more of Apalachicola's finest every day (or every day in every month with an "r" in it anyway). You'll be getting plenty of good nutrition, obviously, but all that zinc can produce problems. A daily intake of 45 mg of zinc (the amount used in the Wayne State study) will be just fine for most people. But studies show that men who get more than 100 mg of zinc per day over a long period of time may raise their risk of prostate cancer and urinary infection. Women have a slightly lesser risk of urinary infection from prolonged high zinc intake. Talk to your doctor or a healthcare professional before starting a zinc supplement regimen to alleviate the risk of infection.
Sources:
"Zinc Supplementation Decreases Incidence of Infections in the Elderly: Effect of Zinc on Generation of Cytokines and Oxidative Stress" American Journal of Clinical Nutrition, Vol. 85, No. 3, March 2007, ajcn.org
"Zinc Pills may Cut Infections in the Elderly" Stephen Daniells, NutraIngredients, 3/29/07, nutraingredients.com
"No Scientific Evidence Diet Supplements Slow Aging" Caleb Hellerman, CNN, 4/10/07, cnn.com
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